Stressor Identification Guidance Document

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EPA has made availabile the Stressor Identification Guidance Document (EPA 822-B-00-025) published under the authority of Section 304(a)(2) of the Clean Water Act (CWA). This technical guidance document is designed to assist water quality managers in identifying unknown causes of biological impairments in any type of water body. Section 101(a) of the Clean Water Act states that it is the objective of the Act to restore and maintain the chemical, physical and biological integrity of the Nation's waters. To achieve this objective, numerous States and Tribes are using biological assessments and biocriteria to help protect the Nation's waters. Using these tools, State and Tribal water quality experts are finding water bodies where the fish, invertebrate, algae or plant communities (or other aquatic life) have been detrimentally impacted by different singular or multiple causes. In many cases, the cause, or causes, of these biological impairments have not yet been identified. The Stressor Identification Guidance Document provides a logical, scientific process by which State, Tribal, and other water quality experts can evaluate available information to identify the stressor(s) causing the biological impairments.

The process has three main steps: (1) List candidate causes of impairment, (2) analyze the evidence, and (3) characterize the causes. When evidence is adequate, using this guidance, investigators should be able to successfully identify the likely cause, or causes. This guidance will also help investigators identify where evidence is weak or lacking and needs to be developed to be able to successfully identify the stressor(s). Once the causes of the biological impairments are identified, water resource managers will be better able to locate the sources of the stressor, or stressors, and take management actions aimed at improving the biological condition of the water body.

This guidance is advisory in nature and its use is not mandatory. As such this guidance does not impose legally-binding requirements on EPA, the States, Tribes, industry, the public or any other entity.

Paper copies can be obtained from the U.S. EPA, Water Resource Center by phone at: (202) 260-7786, or by sending an e-mail to the Center at center.water-resource@epa.gov, or through conventional mail by sending a letter of request to:

U.S. EPA Water Resource Center

Ariel Rios Building,

1200 Pennsylvania Ave.

Washington, DC 20460.

Copies of the document may also be obtained from:

U.S. EPA National Center for Environmental Publications and Information (NCEPI)